Phase separation in poly(ethylene glycol)/poly(lactic acid) blends

Studies were conducted on the morphology of poly(ethylene glycol)/poly(lactic acid) (PEG/PLA) blends. Mixtures comprising PLA and PEG chains of different molecular weights (1500, 3400, 6000 and 35,000) were prepared; their structures were investigated by DSC studies and i.r. spectroscopy. The results suggest that, whenever one of the components is present at more than 20% by wt, it is able to crystallize; such blends consist of two semi-miscible crystalline phases dispersed in an amorphous matrix. For more extreme compositions, only the major component is able to crystallize; the noncrystalline matrix which develops, consists of the minor constituent and the amorphous phase of the major component of the blend. The molecular weight of PEG affects the morphology generated due to the enhanced crystallizability of the longer PEG chains. Crystallization phenomena are viewed as a fundamental driving force for microphase segregation.